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      <title>JVM的内存模型 - 交互式测验</title>
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      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>JVM的内存模型 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
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      <script>
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  {
    "question": "根据文档描述，JVM的内存结构中，哪些区域是所有线程共享的？",
    "options": [
      "Java虚拟机栈和程序计数器",
      "堆和方法区",
      "堆和本地方法栈",
      "方法区和Java虚拟机栈"
    ],
    "correctAnswerIndex": 1,
    "explanation": "JVM内存结构中，堆（Heap）用于存储所有对象实例和数组，方法区（Method Area）用于存储类信息、常量、静态变量等。这两个区域是被所有线程共享的。而Java虚拟机栈、本地方法栈和程序计数器都是线程私有的，每个线程都有一份独立的拷贝。",
    "source": "文档中「JVM 内存结构」部分的「4. 堆（Heap）」和「5. 方法区（Method Area）」小节。",
    "hint": "想一想，哪些数据需要被多个线程访问，比如对象实例和类信息？而哪些数据只与单个线程的执行流相关？"
  },
  {
    "question": "关于程序计数器（Program Counter Register），文档中提到了它的一个非常独特的特性是什么？",
    "options": [
      "它专门用于存储对象实例的引用地址",
      "它是所有线程共享的，用于协调线程执行顺序",
      "它是唯一一个在JVM规范中不会发生 OutOfMemoryError 的内存区域",
      "它的大小是动态变化的，以适应不同方法的执行需求"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档明确指出，程序计数器是JVM内存模型中非常小的一块区域，也是唯一一个不会发生 OutOfMemoryError 的内存区域。它的作用是存储当前线程执行的字节码指令地址，是线程私有的。",
    "source": "文档中「JVM 内存结构」部分的「1. 程序计数器（Program Counter Register）」小节。",
    "hint": "在JVM的各个内存区域中，几乎所有区域都有可能耗尽内存，但有一个区域的职责非常简单和固定，因此不会出现内存溢出问题。"
  },
  {
    "question": "在JVM的堆内存分配策略中，新创建的对象通常最先被分配在哪个区域？",
    "options": [
      "老年代（Old Generation）",
      "新生代的Eden区",
      "新生代的Survivor区",
      "方法区（Method Area）"
    ],
    "correctAnswerIndex": 1,
    "explanation": "根据堆的分代策略，绝大多数新创建的对象会被优先分配在新生代的Eden区。当Eden区空间不足时，会触发一次Minor GC，存活下来的对象会被移动到Survivor区。经历多次GC仍然存活的对象最终会被晋升到老年代。",
    "source": "文档中「内存分配」部分的「2. 堆上的内存分配」小节。",
    "hint": "JVM的堆内存分配策略遵循“朝生夕死”的特点，为新对象设立了一个“出生地”。"
  },
  {
    "question": "文档中提到的哪种垃圾回收算法，虽然回收效率较高，但会造成空间利用率较低，通常被用于新生代的垃圾回收？",
    "options": [
      "标记-清除（Mark-Sweep）",
      "标记-整理（Mark-Compact）",
      "复制（Copying）",
      "分代收集（Generational GC）"
    ],
    "correctAnswerIndex": 2,
    "explanation": "复制（Copying）算法将内存分为两个相等的区域，每次只使用其中一个。当进行垃圾回收时，它会将存活的对象从当前区域复制到另一个空闲区域，然后清空当前区域。这种方式实现简单、效率高，没有内存碎片，但代价是牺牲了一半的内存空间，因此特别适合对象存活率低的新生代。",
    "source": "文档中「内存回收」部分的「1. 垃圾回收机制」小节。",
    "hint": "思考哪种算法需要一个额外的“备用空间”来移动存活的对象。"
  },
  {
    "question": "Java内存模型（JMM）主要为了解决多线程环境下的哪两个核心问题？",
    "options": [
      "内存泄漏和栈溢出",
      "缓存一致性和指令重排序",
      "线程死锁和资源竞争",
      "自动垃圾回收和对象分配"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出，Java内存模型（JMM）是一个抽象概念，它定义了多线程环境下内存访问的规则，主要解决了两个问题：1. 缓存一致性，即确保一个线程对共享变量的修改能被其他线程及时看到；2. 指令重排序，即规范编译器和处理器为了优化性能而对指令顺序进行的调整，以保证多线程程序的正确性。",
    "source": "文档中「内存模型与多线程」部分的「1. 内存模型的基本概念」小节。",
    "hint": "JMM关注的是底层硬件和编译器优化可能给并发编程带来的挑战。"
  },
  {
    "question": "根据文档，`volatile`关键字在多线程编程中提供了哪两项关键保证？",
    "options": [
      "原子性和互斥性",
      "可见性和有序性（禁止指令重排序）",
      "持久性和隔离性",
      "线程安全和高性能"
    ],
    "correctAnswerIndex": 1,
    "explanation": "`volatile`是Java提供的一种轻量级同步机制。它能保证：1. 可见性：当一个线程修改了volatile变量的值，新值会立即被写回主内存，其他线程读取时能立刻看到这个新值。2. 有序性：通过禁止指令重排序，确保volatile变量的读写操作与周围的其他内存操作的相对顺序。",
    "source": "文档中「内存模型与多线程」部分的「2. 内存模型与 volatile 关键字」小节。",
    "hint": "这个关键字确保了当一个线程修改了某个值后，其他线程能“看到”这个修改，并且它的相关操作不会被“乱序执行”。"
  },
  {
    "question": "在Happens-Before原则中，“volatile变量规则”是如何定义的？",
    "options": [
      "对一个volatile变量的读操作 happens-before 后续对这个变量的写操作。",
      "对一个volatile变量的写操作 happens-before 后续对这个变量的读操作。",
      "对任意两个volatile变量的操作，在程序中的顺序决定了它们的happens-before关系。",
      "一个线程对volatile变量的写操作，对于其他线程是不可见的。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "Happens-Before原则中的“volatile变量规则”规定：对一个volatile变量的写操作，先行发生于（happens-before）后续对这个变量的任何读操作。这个规则是volatile实现可见性的关键，确保了写操作的结果对后续的读操作是可见的。",
    "source": "文档中「内存模型与多线程」部分的「4. Happens-Before 原则」小节。",
    "hint": "为了保证可见性，写操作的结果必须对后续的读操作可见，思考一下它们之间的先后顺序关系。"
  }
];
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            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
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                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
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                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
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                '<div class="score-card score-details">' +
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                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
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        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  